1. Field of the Invention
The present invention relates to a locking mechanism of a linear motor travel slider used in a processing machine, such as machine tools or industrial machinery, and to a processing machine having the same. More specifically, the invention relates to a locking mechanism capable of surely locking the travel slider in a stop state of a linear motor during a power failure, and a processing machine having the same.
2. Background Art
Generally, a grinding machine is constructed so that a grinding wheel stock is mounted on a bed reciprocably in a backward and forward direction and a grinding wheel mounted in the grinding wheel stock is reciprocated in the backward and forward direction toward a rotating workpiece supported in a main spindle stock and a tailstock. A linear motor is used as a driving source for driving the grinding wheel stock in the backward and forward direction. This linear motor can be suddenly stopped or suddenly decelerated electrically without using a mechanical brake under control of a controller. In case that an accident such as a power failure or a break in wire occurs during an action of the linear motor and a signal for controlling the linear motor disappears, there is a possibility that an operation by the controller is disabled and the grinding wheel stock coasts.
In order to solve the problem described above, a mechanical brake mechanism of a linear motor travel shaft disclosed in JP-A-10-112971 is proposed. In this brake mechanism, a suction plate is sucked and held in a lower surface of a travel slider through an electromagnet for suction plate holding. A coil spring is interposed between the travel slider and the suction plate, and an air cylinder mechanism is mounted between the travel slider and the suction plate. Further, in an upper surface of a machine stock frame, a fixed magnet is arranged in correspondence with the suction plate and a friction member 5 is attached to a lower surface of the suction plate and an external friction engagement member is laid on the upper surface of the machine stock frame corresponding to this friction member so as to extend in a travel direction of the travel slider.
Then, when the linear motor is energized, the air cylinder upward lifts the suction plate against energization force of the coil spring and the brake mechanism is released. In a state of a power failure, the air cylinder mechanism is stopped and the friction member is pressed on the external friction engagement member by an urging force of the coil spring and braking force is given to the travel slider in travel and coasting of the travel slider is blocked.